Project Summary/Abstract The goal of this new R01 proposal is to investigate the novel role and mechanisms of N6- methyladenosine (m6A) modification of HIV-1 RNA in viral infection. The internal m6A modification of cellular RNA is a newly emerging mechanism of post-transcriptional control of gene expression, which is coordinately regulated by three groups of host proteins, including adenosine methyltransferases (writers), m6A demethylases (erasers), and m6A-selective- binding proteins (readers). Binding of m6A-modified cellular RNA by the readers, YTH domain family proteins (YTHDF1, 2, and 3), can significantly affect various aspects of RNA functions during translation. However, it is unknown whether HIV-1 RNA contains m6A modification and whether the modification regulates viral replication in CD4+ T-cells. We recently identified multiple regions of m6A modification in HIV-1 genomic RNA (gRNA) bound by the readers (YTHDF1-3 proteins) in HIV-1-infected cells. Our data showed that the expression levels of the readers can significantly modulated HIV-1 postentry infection in target cells. Moreover, knockdown of the m6A writers or an eraser in virus producer cells significantly affected HIV-1 Gag protein synthesis and viral release, suggesting the importance of m6A modification of HIV-1 RNA in viral production. Thus, we hypothesize that m6A modification of HIV-1 RNA regulates viral replication in cells by engaging the m6A readers, writers, and erasers, which can have negative or positive impacts on different stages of the HIV-1 lifecycle. We will test the overall hypothesis in three specific aims mainly using primary CD4+ T-cells. Aim 1. To examine the role of HIV-1 RNA m6A modification in viral infection and the mechanisms of m6A reader-mediated viral inhibition; Aim 2. To investigate the role and mechanisms of the m6A writers in regulating HIV-1 infection; and Aim 3. To investigate the role and mechanisms of the m6A erasers in regulating HIV-1 infection. Overall impact: Accomplishing these proposed studies will reveal the novel role and mechanisms of m6A modification of HIV-1 RNA in regulating viral infection in cells. Studying the m6A modification of HIV-1 RNA and its interactions with host proteins represents a new area of HIV-1 RNA biology, which can facilitate therapeutic development against HIV-1 infection.